The present invention relates to a positive photoresist composition for use in the production of semiconductor IC elements, masks for IC production, printed circuit boards, liquid-crystal panels, etc.
Conventional resists comprising a novolak and a naphthoquinonediazide compound are unsuitable for use in pattern formation by lithography using far ultraviolet rays or excimer laser beams, because the novolak and the naphthoquinonediazide show intense absorption in the far ultraviolet region to render the light less apt to reach the resist bottom. Thus, the resist has low sensitivity to give only a tapered pattern.
One means for eliminating the above problem is the chemically amplified resist composition described in, e.g., U.S. Pat. No. 4,491,628 and European Patent 29,139. A chemically amplified positive resist composition is a pattern-forming material in which an acid generates in exposed areas upon irradiation with a radiation such as far ultraviolet rays and this acid catalyzes a reaction that makes the areas irradiated with the actinic rays and the unirradiated areas to differ in solubility in a developing solution to thereby form a pattern on a substrate.
Examples thereof include combinations of a compound which generates an acid upon photodecomposition with an acetal or O,N-acetal compound (see JP-A-48-89003; the term xe2x80x9cJP-Axe2x80x9d as used herein means an xe2x80x9cunexamined published Japanese patent applicationxe2x80x9d), with an orthoester or amidoacetal compound (see JP-A-51-120714), with a polymer having acetal or ketal groups in the backbone (see JP-A-53-133429), with an enol ether compound (see JP-A-55-12995), with an N-acyliminocarbonic acid compound (see JP-A-55-126236), with a polymer having orthoester groups in the backbone (see JP-A-56-17345), with a tertiary alkyl ester compound (see JP-A-60-3625), with a silyl ester compound (see JP-A-60-10247), and with a silyl ether compound (see JP-A-60-37549 and JP-A-60-121446). These combinations show high photosensitivity since they have a quantum efficiency exceeding 1 as the principle.
Another means for eliminating the problem described hereinabove is a system which is stable over long at room temperature but decomposes upon heating in the presence of an acid to become alkali-soluble. Examples thereof include systems comprising a combination of a compound which generates an acid upon exposure to light with an ester having a tertiary or secondary carbon (e.g., t-butyl or 2-cyclohexenyl) or with a carbonic ester compound, as described in, e.g., JP-A-59-45439, JP-A-60-3625, JP-A-62-229242, JP-A-63-27829, JP-A-63-36240, JP-A-63-250642; Polym. Eng. Sce., Vol. 23, p. 12 (1983); ACS. Sym., Vol. 242, p. 11 (1984); Semiconductor World, November 1987 issue, p. 91; Macromolecules, Vol. 21, p. 1475 (1988); and SPIE, Vol. 920, p. 42 (1988). Since these systems also have high sensitivity and show reduced absorption in the deep UV region as compared with the naphthoquinonediazide/novolak resin systems, they can be effective systems for coping with the utilization of the light source having shorter wavelength.
The chemically amplified positive resist compositions described above are roughly divided into three groups: three-component systems comprising an alkali-soluble resin, a compound which generates an acid upon exposure to a radiation (photo-acid generator), and a dissolution inhibitive compound for the alkali-soluble resin which has acid-decomposable groups; two-component systems comprising a resin having groups which decompose upon reaction with an acid to render the resin alkali-soluble and a photo-acid generator; and hybrid systems comprising a resin having groups which decompose upon reaction with an acid to render the resin alkali-soluble, a low-molecular dissolution inhibitive compound having an acid-decomposable group, and a photo-acid generator.
In JP-A-2-19847 is disclosed a resist composition characterized by containing a resin obtained from poly(p-hydroxystyrene) by protecting all or part of the phenolic hydroxyl groups each with a tetrahydropyranyl group.
In JP-A-4-219757 is disclosed a resist composition characterized by containing a resin obtained likewise from poly(p-hydroxystyrene) by replacing from 20 to 70% of the phenolic hydroxyl groups each with an acetal group.
Moreover, JP-A-5-249682 discloses a photoresist composition containing a similar resin protected with an acetal. In JP-A-8-123032 is disclosed a photoresist composition containing a terpolymer having groups substituted with acetal groups.
Furthermore, JP-A-8-253534 discloses a photoresist composition containing a partly crosslinked polymer having groups substituted with acetal groups.
JP-A-8-15864 discloses a positive resist composition comprising a mixture comprising as a resin component polyhydroxystyrene in which 10 to 60 mol % of hydroxy groups were replaced with t-butoxycarbonyloxy groups and polyhydroxystyrene in which 10 to 60 mol % of hydroxy groups were replaced with ethoxyethoxy groups.
However, these compositions have some problems such as unsatisfactory dimensional reproducibility of isolated patterns and generation of scum at lower parts of patterns after development. Solution of these problems has been desired.
An object of the present invention is to provide an excellent, chemically amplified positive photoresist composition which has high resolution and improved dimensional reproducibility of isolated patterns.
Another object of the present invention is to provide an excellent, chemically amplified positive photoresist composition which is prevented from generating a scum after development and has high resolution.
As a result of intensive investigations made by the present inventor under these circumstances, it has been found that a positive photoresist composition comprising a combination of two alkali-soluble resin binders each having a substituent having a different specific structure from each other, a compound which generates an acid upon irradiation with actinic rays or a radiation, and a solvent (first photoresist composition) shows high resolution and is effective in eliminating the above-described problem concerning the dimensional reproducibility of isolated patterns, and a positive photoresist composition comprising a combination of an alkali-soluble resin binder substituted with substituents of a specific structure and a nonpolymeric dissolution inhibitive compound having specific functional groups, a compound which generates an acid upon irradiation with actinic rays or a radiation, and a solvent (second photoresist composition) shows high resolution and is effective in eliminating the problem of scum generation described above. The present invention has been completed based on these findings.
(1) The first positive photoresist composition comprises:
(a) Resin A obtained from an alkali-soluble resin containing phenolic hydroxyl groups by replacing from 10 to 80% of the phenolic hydroxyl groups each with a group represented by the following formula (I); (b) Resin B obtained from an alkali-soluble resin containing phenolic hydroxyl groups by replacing from 10 to 80% of the phenolic hydroxyl groups each with a group represented by the following formula (II) or (III); (c) a compound which generates an acid upon irradiation with actinic rays or a radiation; and (d) a solvent, 
xe2x80x83wherein R1 represents a substituent selected from alkyl groups having 1 to 4 carbon atoms; W represents either an organic residue containing at least one atom selected from oxygen, nitrogen, sulfur, phosphorus, and silicon atoms or an atomic group selected from the group consisting of an amino group, an ammonium group, and a mercapto group;
n represents a natural number of from 1 to 4; and
R4 represents a linear, branched, or cyclic alkyl group having 1 to 6 carbon atoms.
(2) The second positive photoresist composition comprises:
(a) Resin A obtained from an alkali-soluble resin containing phenolic hydroxyl groups by replacing from 10 to 80% of the phenolic hydroxyl groups each with a group represented by formula (I);
(b) a nonpolymeric dissolution inhibitive compound which has at least one kind of group selected from tertiary alkyl ester groups and tertiary alkyl carbonate groups, and is capable of enhancing solubility in aqueous alkali solutions by the action of an acid;
(c) a compound which generates an acid upon irradiation with actinic rays or a radiation; and
(d) a solvent, 
xe2x80x83wherein R1 represents a substituent selected from alkyl groups having 1 to 4 carbon atoms; W represents either an organic group containing at least one atom selected from oxygen, nitrogen, sulfur, phosphorus, and silicon atoms or an atomic group selected from the group consisting of an amino group, an ammonium group, and a mercapto group; and n represents a natural number of from 1 to 4.
(3) The positive photoresist composition as described in (1) or (2) above, wherein W in formula (I) for component (a) is a group selected from the group consisting of the following substituents:
W: 
xe2x80x83wherein
R2 represents a hydrogen atom or a substituent selected from the group consisting of a linear, branched, or cyclic alkyl group having 1 to 6 carbon atoms, a linear, branched, or cyclic alkenyl group having 2 to 6 carbon atoms, a substituted or unsubstituted aryl group, and a substituted or unsubstituted aralkyl group;
R3 represents a hydrogen atom or a substituent selected from the group consisting of a linear, branched, or cyclic alkyl group having 1 to 6 carbon atoms, a linear, branched, or cyclic alkoxy group having 1 to 6 carbon atoms, a halogen atom, a nitro group, an amino group, a hydroxyl group, and a cyano group;
X represents a halogen atom; and m represents a natural number of from 1 to 4.
(4) The positive photoresist composition as described in (1), (2) or (3), wherein the alkali-soluble resin containing phenolic hydroxyl groups used for Resin A and/or Resin B is poly(p-hydroxystyrene).
The present invention will be explained below in detail.
The alkali-soluble resin having phenolic hydroxyl groups used for the present invention is preferably a copolymer of o-, m-, or p-hydroxystyrene (these are inclusively referred to as hydroxystyrenes) or o-, m-, or p-hydroxy-xcex1-methylstyrene (these are inclusively referred to as hydroxy-xcex1-methylstyrenes) in which the content of repeating units derived from the styrene derivative is at least 30 mol %, preferably at least 50 mol %, a homopolymer of any of these styrene derivatives, or a resin obtained by partially hydrogenating the benzene nuclei of those units of the copolymer or homopolymer. More preferred is a homopolymer of p-hydroxystyrene. Preferred examples of monomers used for copolymerization in producing the above copolymer, besides the hydroxystyrenes and the hydroxy-xcex1-methylstyrenes, include acrylic esters, methacrylic esters, acrylamide and analogues thereof, methacrylamide and analogues thereof, acrylonitrile, methacrylonitrile, maleic anhydride, styrene, xcex1-methylstyrene, acetoxystyrene, and alkoxystyrenes. More preferred are styrene, acetoxystyrene, and t-butoxystyrene.
This alkali-soluble resin has a weight-average molecular weight in the range of preferably from 3,000 to 80,000, more preferably from 7,000 to 50,000. The molecular weight distribution (Mw/Mn) thereof is in the range of generally from 1.01 to 4.0, preferably from 1.05 to 1.20. A polymerization technique such as anionic polymerization is preferably used for obtaining a polymer having such a molecular weight distribution.
In the present invention, it is essential to use Resin A obtained from the alkali-soluble resin containing phenolic hydroxyl groups by replacing from 10 to 80% of the phenolic hydroxyl groups each with a group represented by formula (I) given above.
In formula (I), R1 represents a substituent selected from alkyl groups having 1 to 4 carbon atoms.
W represents either an organic group containing at least one atom selected from oxygen, nitrogen, sulfur, phosphorus, and silicon atoms or an atomic group selected from the group consisting of an amino group, an ammonium group, and a mercapto group.
Furthermore, n represents a natural number of from 1 to 4, preferably 2 or 3.
Preferred examples of R1 include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, and t-butyl. More preferred is methyl.
The organic group represented by W comprises at least one atom selected from oxygen, nitrogen, sulfur, phosphorus, and silicon atoms and at least one carbon atom.
Preferred examples of W include groups represented by the following formulae. 
In the above formulae,
R2 represents or R2""s each independently represents a hydrogen atom or a substituent selected from the group consisting of a linear, branched, or cyclic alkyl group having 1 to 6 carbon atoms, a linear, branched, or cyclic alkenyl group having 2 to 6 carbon atoms, a substituted or unsubstituted aryl group having 6 to 12 carbon atoms, and a substituted or unsubstituted aralkyl group having 7 to 13 carbon atoms;
R3 represents or R3""s each independently represents a hydrogen atom or a substituent selected from the group consisting of a linear, branched, or cyclic alkyl group having 1 to 6 carbon atoms, a linear, branched, or cyclic alkoxy group having 1 to 6 carbon atoms, a halogen atom, a nitro group, an amino group, a hydroxyl group, and a cyano group;
X represents a halogen atom; and
m represents a natural number of from 1 to 4, preferably 1 or 2.
Preferred examples of the linear, branched, or cyclic alkyl group having 1 to 6 carbon atoms which is represented by R2 or R3 include methyl, ethyl, n-propyl, isopropyl, cyclopropyl, n-butyl, isobutyl, sec-butyl, t-butyl, pentyl, isopentyl, neopentyl, cyclopentyl, hexyl, and cyclohexyl. More preferred are methyl and ethyl.
Preferred examples of the linear, branched, or cyclic alkenyl group having 2 to 6 carbon atoms which is represented by R2 include vinyl, 1-propenyl, allyl, isopropenyl, 1-butenyl, 2-butenyl, 2-pentenyl, and cyclohexenyl. More preferred are vinyl and isopropenyl.
Preferred examples of the aryl group having 6 to 12 carbon atoms include phenyl, tolyl, xylyl, mesityl, and cumenyl, with phenyl being more preferred. Preferred examples of the aralkyl group having 7 to 13 carbon atoms include benzyl, phenethyl, xcex1-methylbenzyl, and benzhydryl, with benzyl being more preferred.
These aryl and aralkyl groups may have one or more substituents selected from halogen atoms, nitro, alkoxy, acetyl, amino, ester, and amido groups, and the like.
Preferred examples of the linear, branched, or cyclic alkoxy group having 1 to 6 carbon atoms which is represented by R3 include methoxy, ethoxy, propoxy, isopropoxy, butoxy, pentyloxy, and hexyloxy. More preferred are methoxy and ethoxy.
Preferred examples of the halogen atom include fluorine, chlorine, bromine, and iodine. More preferred are chlorine and bromine.
As shown above, W may be a cyano or formyl group.
Specific examples of formula (I) are given below. However, formula (I) should not be construed as being limited to these examples, in which Me, Et, and Ph represent methyl, ethyl, and phenyl, respectively. 
Resin A, having the substituents described above, can be obtained by synthesizing the vinyl ether corresponding to the substituents and reacting the ether by a known method with an alkali-soluble resin containing phenolic hydroxyl groups which has been dissolved in an appropriate solvent, e.g., tetrahydrofuran. This reaction is usually conducted in the presence of an acid catalyst, preferably an acid ion-exchange resin, hydrochloric acid, or p-toluenesulfonic acid, or a salt such as pyridinium tosylate. The corresponding vinyl ether can be synthesized from an active starting material such as chloroethyl vinyl ether through a nucleophilic substitution reaction or the like.
Specific examples of the structure of Resin A are shown below. However, Resin A for use in the present invention should not be construed as being limited to these examples, in which Me represents methyl, Et ethyl, Ph phenyl, tBu t-butyl, and Ac acetyl. 
In Resin B according to the present invention, the substituent R4 in formula (II) or (III) given above is an alkyl group having 1 to 6 carbon atoms, specifically, a linear, branched, or cyclic alkyl group having 1 to 6 carbon atoms. Examples thereof include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, t-butyl, n-pentyl, isopentyl, neopentyl, t-pentyl, cyclopentyl, n-hexyl, isohexyl, and cyclohexyl. Preferred among these are tertiary alkyl groups such as t-butyl and t-pentyl.
Specific examples of the structure of Resin B are shown below. However, Resin B for use in the present invention should not be construed as being limited to these examples, in which Me represents methyl, Et ethyl, Ph phenyl, tBu t-butyl, and Ac acetyl. 
In Resin A contained in the first composition according to the present invention, from 10 to 80%, preferably from 15 to 60%, more preferably from 20 to 40%, of the phenolic hydroxyl groups of the alkali-soluble resin should have been replaced with substituents represented by formula (I).
If the degree of replacement of the phenolic hydroxyl groups with substituents represented by formula (I) is lower than 10%, a sufficient difference in the rate of dissolution in alkali cannot be obtained between exposed and unexposed areas, resulting in reduced resolution. If the degree of that replacement exceeds 80%, especially heat resistance decreases. Thus, such too high and too low degrees of replacement are unsuitable for the present invention.
Like Resin A, Resin B according to the present invention should be one in which from 10 to 80%, preferably from 15 to 60%, more preferably from 20 to 40%, of the phenolic hydroxyl groups of the alkali-soluble resin have been replaced with substituents represented by formula (II) or (III).
If the degree of replacement of the phenolic hydroxyl groups with substituents represented by formula (II) or (III) is lower than 10%, a sufficient difference in the rate of dissolution in alkali cannot be obtained between exposed and unexposed areas, resulting in reduced resolution. If the degree of that replacement exceeds 80%, especially heat resistance decreases. Thus, such too high and too low degrees of replacement are unsuitable for the present invention.
Resin B in the present invention may contain both or either of substituents represented by formula (II) and substituents represented by formula (III).
Resin A according to the present invention, which is obtained by protecting phenolic hydroxyl groups (alkali-soluble groups) of an alkali-soluble resin with specific acid-decomposable groups represented by formula (I), produces remarkable effects when used in combination with Resin B, which has been protected with specific acid-decomposable groups represented by formula (II) or (III).
Resin B can be synthesized by the following methods. In the case where substituents represented by formula (II) are introduced into an alkali-soluble resin containing phenolic hydroxyl groups, this is accomplished by reacting the alkali-soluble resin with, for example, t-butyl bromoacetate by a known method to replace part of the phenolic hydroxyl groups with t-butyl ester groups, thereby giving Resin B. In the case where substituents represented by formula (III) are introduced into the alkali-soluble resin, this is accomplished by reacting the alkali-soluble resin with, for example, di-t-butyl dicarbonate by a known method to replace part of the phenolic hydroxyl groups with t-butoxycarbonyloxy groups, thereby giving Resin B.
In the present invention, Resin A and Resin B each has a weight-average molecular weight of preferably from 3,000 to 80,000, more preferably from 7,000 to 50,000. The molecular weight distribution (Mw/Mn) thereof is in the range of generally from 1.01 to 4.0, preferably from 1.05 to 1.20.
The use of Resin A and Resin B in combination, as in the present invention, is novel. The protective groups represented by formulae (I), (II), and (III) contained in these resins decompose by the action of an acid and thus function to enhance solubility of each resin in an alkaline developing solution.
In the composition of the present invention, the mixing weight ratio of Resin A to Resin B (A/B) is preferably from 20/80 to 80/20, more preferably from 30/70 to 70/30, most preferably from 40/60 to 60/40.
By blending these two resins, each having a specific structure, in a specific mixing ratio, a positive photoresist composition having the desired performances is obtained.
On the other hand, in the second composition according to the present invention, Resin A should be one in which from 10 to 80%, preferably from 10 to 60%, more preferably from 10 to 40%, of the phenolic hydroxyl groups of the alkali-soluble resin should have been replaced with substituents represented by formula (I).
If the degree of replacement of the phenolic hydroxyl groups with substituents represented by formula (I) is lower than 10%, a sufficient difference in the rate of dissolution in alkali cannot be obtained between exposed and unexposed areas, resulting in reduced resolution. If the degree of that replacement exceeds 80%, especially heat resistance decreases. Thus, such too high and too low degrees of replacement are unsuitable for the present invention.
Resin A, which is obtained by protecting phenolic hydroxyl groups (alkali-soluble groups) of an alkali-soluble resin with specific acid-decomposable groups represented by formula (I), produces remarkable effects when used in combination with a nonpolymeric dissolution inhibitive compound.
The second composition according to the present invention should further contain a nonpolymeric dissolution inhibitive compound which has at least one kind of group selected from tertiary alkyl ester groups and tertiary alkyl carbonate groups and capable of increasing the solubility of the resin in aqueous alkali solutions by the action of an acid.
The nonpolymeric dissolution inhibitive compound means a compound which has a structure formed by incorporating one or more acid-decomposable groups selected from those mentioned above into a compound having a certain molecular weight not higher than 3,000 and having a single structure, and which becomes alkali-soluble by the action of an acid. This nonpolymeric dissolution inhibitive compound preferably has, per molecule, three or more groups decomposable by an acid and becomes alkali-soluble upon decomposition of these groups.
In the present invention, the resin and nonpolymeric dissolution inhibitive compound described above can be used in combination with an alkali-soluble resin containing no acid-decomposable groups.
The nonpolymeric dissolution inhibitive compound, component (b), used in the present invention has at least one kind of acid-decomposable group selected from tertiary alkyl ester groups and tertiary alkyl carbonate groups, and may have these two kinds of groups in combination. It is advantageous to use a compound in which each structure has at least two acid-decomposable groups and the two acid-decomposable groups most apart from each other are separated from each other by at least 10, preferably at least 11, more preferably at least 12 bonding atoms excluding those contained in the acid-decomposable groups, or to use a compound in which each structure has at least three acid-decomposable groups and the two acid-decomposable groups most apart from each other are separated from each other by at least 9, preferably at least 10, more preferably at least 11 bonding atoms excluding those contained in the acid-decomposable groups.
The nonpolymeric dissolution inhibitive compound inhibits the dissolution of the alkali-soluble resin in an alkali, but upon exposure to light it functions to accelerate the dissolution of the resin in an alkali because the protective acid-decomposable groups thereof are eliminated by an acid generated upon exposure. Although dissolution inhibitive compounds having the skeletons of naphthalene, biphenyl, and a diphenylcycloalkane are disclosed in JP-A-63-27829 (the term xe2x80x9cJP-Axe2x80x9d as used herein means an xe2x80x9cunexamined published Japanese patent applicationxe2x80x9d) and JP-A-3-198059, these compounds are less effective in inhibiting the dissolution of alkali-soluble resins and are insufficient in profile and resolution.
Preferred examples of the nonpolymeric dissolution inhibitive compound for use in the present invention include a compound obtained from a single-structure compound having a molecular weight of 3,000 or lower and containing three or more alkali-soluble groups per molecule by protecting at least half of the alkali-soluble groups with acid-decomposable groups selected from the aforementioned ones. Use of such a nonpolymeric dissolution inhibitive compound containing alkali-soluble groups remaining unprotected is advantageous in that it has improved solubility in solvents and thus enhances the effects of the invention.
In the present invention, the upper limit of the number of those bonding atoms is preferably 50, more preferably 30.
The nonpolymeric dissolution inhibitive compound for use in the present invention has a significantly improved dissolution inhibitive effect on the alkali-soluble resin when it has three or more, preferably four or more acid-decomposable groups, or when it has two acid-decomposable groups and these acid-decomposable groups are apart from each other at not less than a certain distance.
The distance between acid-decomposable groups in the present invention is expressed in terms of the number of bonding atoms present between the groups, excluding the atoms contained in the groups. For example, in each of compounds (1) and (2) shown below, the distance between acid-decomposable groups is 4 bonding atoms. In compound (3), that distance is 12 bonding atoms. 
Although the acid-decomposable dissolution inhibitive compound for use in the present invention may have two or more acid-decomposable groups on the same benzene ring, it is preferably a compound having a framework in which each benzene ring does not have more than one acid-decomposable group. The molecular weight of the acid-decomposable dissolution inhibitive compound for use in the present invention is 3,000 or lower, preferably from 500 to 3,000, more preferably from 1,000 to 2,500.
In a preferred embodiment of the present invention, the acid-decomposable group is bonded to the compound in the form of the structure represented by xe2x80x94COOxe2x80x94C(R01)(R02)(R03) or xe2x80x94Oxe2x80x94COxe2x80x94Oxe2x80x94C(R01)(R02)(R03), more preferably the structure represented by xe2x80x94R0xe2x80x94COOxe2x80x94C(R01)(R02)(R03) or xe2x80x94Arxe2x80x94Oxe2x80x94COxe2x80x94Oxe2x80x94C(R01)(R02)(R03).
R01, R02, and R03 may be the same or different and each represents an alkyl group, a cycloalkyl group, an alkenyl group, or an aryl group. Two of R01 to R03 may be bonded to each other to form a ring, while it is preferred not to form a ring. R0 and Ar represents an optionally substituted, aliphatic or aromatic hydrocarbon group having a valence of 2 or higher.
The alkyl group is preferably one having 1 to 4 carbon atoms, such as methyl, ethyl, propyl, n-butyl, sec-butyl, or t-butyl. The cycloalkyl group is preferably one having 3 to 10 carbon atoms, such as cyclopropyl, cyclobutyl, cyclohexyl, or adamantyl. The alkenyl group is preferably one having 2 to 4 carbon atoms, such as vinyl, propenyl, allyl, or butenyl. The aryl group is preferably one having 6 to 14 carbon atoms, such as phenyl, xylyl, toluyl, cumenyl, naphthyl, or anthracenyl.
Examples of the substituents include hydroxy, halogen atoms (fluorine, chlorine, bromine, and iodine), nitro, cyano, the alkyl groups enumerated above, alkoxy groups such as methoxy, ethoxy, hydroxyethoxy, propoxy, hydroxypropoxy, n-butoxy, isobutoxy, sec-butoxy, and t-butoxy, alkoxycarbonyl groups such as methoxycarbonyl and ethoxycarbonyl, aralkyl groups such as benzyl, phenethyl, and cumyl, aralkyloxy groups, acyl groups such as formyl, acetyl, butyryl, benzoyl, cyanamyl, and valeryl, acyloxy groups such as butyryloxy, the alkenyl groups enumerated above, alkenyloxy groups such as vinyloxy, propenyloxy, allyloxy, and butenyloxy, the aryl groups enumerated above, aryloxy groups such as phenoxy, and aryloxycarbonyl groups such as benzoyloxy.
Examples of the tertiary alkyl group contained in the tertiary alkyl ester groups and tertiary alkyl carbonate groups include t-butyl, t-pentyl and t-hexyl, and especially, t-butyl.
Examples of the nonpolymeric dissolution inhibitive compound as component (b) include compounds obtained from the polyhydroxy compounds given in the patent documents specified below by protecting part or all of the phenolic OH groups by bonding thereto the tertiary alkyl ester groups and tertiary alkyl carbonate groups; the patent documents include JP-A-1-289946, JP-A-1-289947, JP-A-2-2560, JP-A-3-128959, JP-A-3-158855, JP-A-3-179353, JP-A-3-191351, JP-A-3-200251, JP-A-3-200252, JP-A-3-200253, JP-A-3-200254, JP-A-3-200255, JP-A-3-259149, JP-A-3-279958, JP-A-3-279959, JP-A-4-1650, JP-A-4-1651, JP-A-4-11260, JP-A-4-12356, JP-A-4-12357, and Japanese Patent Applications Nos. 3-33229, 3-230790, 3-320438, 4-25157, 4-52732, 4-103215, 4-104542, 4-107885, 4-107889, and 4-152195.
Preferred of these are the compounds obtained from the polyhydroxy compounds given in JP-A-1-289946, JP-A-3-128959, JP-A-3-158855, JP-A-3-179353, JP-A-3-200251, JP-A-3-200252, JP-A-3-200255, JP-A-3-259149, JP-A-3-279958, JP-A-4-1650, JP-A-4-11260, JP-A-4-12356, JP-A-4-12357, Japanese Patent Applications Nos. 4-25157, 4-103215, 4-104542, 4-107885, 4-107889, and 4-152195.
Specifically, such polyhydroxy compounds are represented by formulae (I) to (XVI). 
In the above formulae,
R101, R102, R108, and R130 may be the same or different and each represents a hydrogen atom, xe2x80x94R0xe2x80x94COOxe2x80x94C(R01)(R02)(R03), or xe2x80x94COxe2x80x94Oxe2x80x94C(R01)(R02)(R03), wherein R0, R01, R02, and R03 have the same meanings as defined hereinabove;
R100 represents xe2x80x94COxe2x80x94, xe2x80x94COOxe2x80x94, xe2x80x94NHCONHxe2x80x94, xe2x80x94NHCOOxe2x80x94, xe2x80x94Oxe2x80x94, xe2x80x94Sxe2x80x94, xe2x80x94SOxe2x80x94, xe2x80x94SO2xe2x80x94, xe2x80x94SO3xe2x80x94, or a group represented by 
xe2x80x83where
G is 2 to 6, provided that when G is 2, at least either of R150 and R151 is an alkyl group,
R150 and R151 may be the same or different and each represents a hydrogen atom, an alkyl group, an alkoxy group, xe2x80x94OH, xe2x80x94COOH, xe2x80x94CN, a halogen atom, xe2x80x94R152xe2x80x94COOR153, or xe2x80x94R154xe2x80x94OH,
R152 and R154 each represents an alkylene group, and
R153 represents a hydrogen atom, an alkyl group, an aryl group, or an aralkyl group;
R99, R103 to R107, R109, R111 to R118, R121 to R123, R128 to R129, R131 to R134, R138 to R141, and R143 may be the same or different and each represents a hydrogen atom, a hydroxyl group, an alkyl group, an alkoxy group, an acyl group, an acyloxy group, an aryl group, an aryloxy group, an aralkyl group, an aralkyloxy group, a halogen atom, a nitro group, a carboxyl group, a cyano group, or xe2x80x94N(R155)(R156) (where R155 and R156 each represents H, an alkyl group, or an aryl group);
R110 represents a single bond, an alkylene group, or a group represented by 
xe2x80x83where
R157 and R159 may be the same or different and each represents a single bond, an alkylene group, xe2x80x94Oxe2x80x94, xe2x80x94Sxe2x80x94, xe2x80x94COxe2x80x94, or a carboxyl group, and
R158 represents a hydrogen atom, an alkyl group, an alkoxy group, an acyl group, an acyloxy group, an aryl group, a nitro group, a hydroxyl group, a cyano group, or a carboxyl group, provided that each hydroxyl group may be replaced by an acid-decomposable group (e.g., t-butoxycarbonylmethyl, tetrahydropyranyl, 1-ethoxy-1-ethyl, or 1-t-butoxy-1-ethyl);
R119 and R120 may be the same or different and each represents a methylene group, a lower-alkyl-substituted methylene group, a halomethylene group, or a haloalkyl group, provided that the term xe2x80x9clower alkylxe2x80x9d herein means an alkyl group having 1 to 4 carbon atoms;
R124 to R127 may be the same or different and each represents a hydrogen atom or an alkyl group;
R135 to R137 may be the same or different and each represents a hydrogen atom, an alkyl group, an alkoxy group, an acyl group, or an acyloxy group;
R142 represents a hydrogen atom, xe2x80x94R0xe2x80x94COOxe2x80x94C(R01)(R02)(R03), xe2x80x94COxe2x80x94Oxe2x80x94C(R01)(R02)(R03), or the group represented by 
R144 and R145 may be the same or different and each represents a hydrogen atom, a lower alkyl group, a lower haloalkyl group, or an aryl group;
R146 to R149 may be the same or different and each represents a hydrogen atom, a hydroxyl group, a halogen atom, a nitro group, a cyano group, a carbonyl group, an alkyl group, an alkoxy group, an alkoxycarbonyl group, an aralkyl group, an aralkyloxy group, an acyl group, an acyloxy group, an alkenyl group, an alkenyloxy group, an aryl group, an aryloxy group, or an aryloxycarbonyl group, provided that the four groups represented by the same symbol need not be the same;
Y represents xe2x80x94COxe2x80x94 or xe2x80x94SO2xe2x80x94;
Z and B each represents a single bond or xe2x80x94Oxe2x80x94;
A represents a methylene group, a lower-alkyl-substituted methylene group, a halomethylene group, or a haloalkyl group;
E represents a single bond or an oxymethylene group;
when any of a to z and a1 to y1 is 2 or a larger integer, the groups in the parentheses may be the same or different;
a to q, s, t, v, g1 to i1, k1 to m1, o1, q1, s1, and u1 each represents 0 or an integer of 1 to 5;
r, u, w, x, y, z, a1 to f1, p1, r1, t1, and v1 to x1 each represents 0 or an integer of 1 to 4;
j1, n1, z1, a2, b2, c2, and d2 each represents 0 or an integer of 1 to 3;
at least one of z1, a2, c2, and d2 is 1 or larger;
y1 is an integer of 3 to 8;
(a+b), (e+f+g), (k+l+m), (q+r+s), (w+x+y), (c1+d1), (g1+h1+i1+j1), (o1+p1), and (s1+t1) each is 2 or larger;
(j1+n1) is 3 or smaller;
(r+u), (w+z), (x+a1), (y+b1), (c1+e1), (d1+f1), (p1+r1), (t1+v1), and (x1+w1) each is 4 or smaller, provided that in general formula (V), (w+z) and (x+a1) each is 5 or smaller; and
(a+c), (b+d), (e+h), (f+i), (g+j), (k+n), (l+o), (m+p), (q+t), (s+v), (g1+k1), (h1+11), (i1+m1), (o1+q1), and (s1+u1) each is 5 or smaller. 
In formula (XIII),
R160 represents an organic group, a single bond, xe2x80x94Sxe2x80x94, xe2x80x94SOxe2x80x94, 
R161 represents a hydrogen atom, a monovalent organic group, or a group represented by 
xe2x80x83where
R162 to R166 may be the same or different and each represents a hydrogen atom, a hydroxyl group, a halogen atom, an alkyl group, an alkoxy group, an alkenyl group, xe2x80x94Oxe2x80x94R0xe2x80x94COOxe2x80x94C(R01)(R02)(R03) or xe2x80x94Oxe2x80x94COxe2x80x94Oxe2x80x94C(R01)(R02)(R03), provided that at least two of R162 to R166 are xe2x80x94Oxe2x80x94R0xe2x80x94COOxe2x80x94C(R01)(R02)(R03) or xe2x80x94Oxe2x80x94COxe2x80x94Oxe2x80x94C(R01)(R02)(R03), and that the four or six substituents represented by the same symbol need not be the same, and
X represents a divalent organic group; and
e2 represents 0 or 1.
In formula (XIV),
R167 to R170 may be the same or different and each represents a hydrogen atom, a hydroxyl group, a halogen atom, an alkyl group, an alkoxy group, or an alkenyl group, provided that the four to six substituents represented by the same symbol need not be the same;
R171 and R172 each represents a hydrogen atom, an alkyl group, or a group represented by 
at least two of R173""s each represents xe2x80x94Oxe2x80x94R0xe2x80x94COOxe2x80x94C(R01)(R02)(R03) or xe2x80x94Oxe2x80x94COxe2x80x94Oxe2x80x94C(R01)(R02)(R03), and the remainder each represents a hydroxyl group;
f2 and h2 each represents 0 or 1; and
g2 represents 0 or an integer of 1 to 4.
In formula (XV),
R174 to R180 may be the same or different and each represents a hydrogen atom, a hydroxyl group, a halogen atom, an alkyl group, an alkoxy group, a nitro group, an alkenyl group, an aryl group, an aralkyl group, an alkoxycarbonyl group, an arylcarbonyl group, an acyloxy group, an acyl group, an aralkyloxy group, or an aryloxy group, provided that the six substituents represented by the same symbol need not be the same; and
at least two of R181""s each represents xe2x80x94Oxe2x80x94R0xe2x80x94COOxe2x80x94C(R01)(R02)(R03) or xe2x80x94Oxe2x80x94COxe2x80x94Oxe2x80x94C(R01)(R02)(R03) and the remainder each represents a hydroxyl group. 
In formula (XVI),
R182 represents a hydrogen atom or an alkyl group, provided that the atoms or groups represented by R182 need not be the same;
R183 to R186 each represents a hydroxyl group, a hydrogen atom, a halogen atom, an alkyl group, or an alkoxy group, provided that the three substituents represented by the same symbol need not be the same; and
at least two of R187""s each represents xe2x80x94Oxe2x80x94R0xe2x80x94COOxe2x80x94C(R01)(R02)(R03) or xe2x80x94Oxe2x80x94COxe2x80x94Oxe2x80x94C(R01)(R02)(R03), and the remainder each represents a hydroxyl group.
Specific examples of the frameworks of preferred compounds are shown below. 
In Compounds (1) to (63), R represents a hydrogen atom, xe2x80x94CH2xe2x80x94COOxe2x80x94C(CH3)2C6H5, xe2x80x94CH2xe2x80x94COOxe2x80x94C(CH3)3, or xe2x80x94COOxe2x80x94C(CH3)3, provided that at least two or, depending on the structure, at least three of R""s are not hydrogen atoms, and that the substituents represented by R need not be the same.
In the case where the non-polymer dissolution inhibitive compound described above is used in the present invention, the addition amount of the dissolution inhibitive compound is from 3 to 50% by weight, preferably from 5 to 35% by weight based on the total amount of all solid components of the photosensitive composition. If the amount is less than 3%, high resolution may not be obtained. If it exceeds 50%, there is a tendency that the storage stability is deteriorated to cause film shrinkage and the heat resistance of the resist is deteriorated.
The first and second compositions can contain an alkali-soluble resin having no acid-decomposable groups. The addition of such an alkali-soluble resin improves the sensitivity. The alkali-soluble resin having no acid-decomposable groups (hereinafter referred to also as xe2x80x9calkali-soluble resinxe2x80x9d) is a resin soluble in an aqueous alkali solution. Preferred examples thereof include polyhydroxystyrenes, novolak resins and derivatives thereof. Copolymers containing p-hydroxystyrene units can be used as long as they are alkali-soluble. Especially preferred are poly(p-hydroxysyrene), poly(p/m-hydroxystyrene) copolymer, poly(p/o-hydroxystyrene) copolymer, and poly(p-hydroxystyrene-styrene) copolymer. Poly(alkyl-substituted hydroxystyrene) resins such as poly(4-hydroxy-3-methylstyrene) resin and poly(4-hydroxy-3,5-dimethylstyrene) resin, and resins prepared by alkylating or acetylating part of phenolic OH groups of the above-described resins are also preferably used as long as they are alkali-soluble.
The resins in which part of phenol nuclei of the above resins (30 mol % or less of the whole phenol nuclei) are hydrogenated have improved transparency and are preferable in sensitivity, resolution and formation of rectangular profile.
Examples of the alkali-soluble resin for use in the present invention include novolak resins, hydrogenated novolak resins, acetone-pyrogallol resins, polyhydroxystyrene, alkyl-substituted polyhydroxystyrene, hydroxystyrene/N-substituted maleimide copolymers, partially O-alkylated poly(hydroxystyrene)s, partially O-acylated poly(hydroxystyrene)s, styrene/maleic anhydride copolymers, carboxylated methacrylic resins, and derivatives thereof, poly(styrene-hydroxystyrene) copolymer, and hydrogenated polyhydroxystyrene. However, the alkali-soluble resin for use in the present invention should not be construed as being limited to these examples.
Particularly preferred alkali-soluble resins include novolak resins, alkali-soluble resins containing p-hydroxystyrene units (preferably poly(p-hydroxystyrene), poly(p/m-hydroxystyrene) copolymer, poly(p/o-hydroxystyrene) copolymer, poly(p-hydroxystyrene-styrene) copolymer, poly(alkyl-substituted hydroxystyrene) resins such as poly(4-hydroxy-3-methylstyrene) resin and poly(4-hydroxy-3,5-dimethylstyrene) resin, and resins prepared by alkylating or acetylating part of phenolic OH groups of the above-described resins, partially hydrogenated polyhydroxystyrene resins, polyhydroxystyrene resins, partially hydrogenated novolak resins, and partially hydrogenated polyhydroxystyrene resins.
The terminology xe2x80x9cpolyhydroxystyrenexe2x80x9d means a polymer obtained by polymerizing at least one monomer selected from the group consisting of p-hydroxystyrene monomer, m-hydroxystyrene monomer, o-hydroxystyrene monomer, and alkyl-substituted hydroxystyrene monomers in which the above-described monomers are substituted by an alkyl group having 1 to 4 carbon atoms at the ortho-position with respect to the hydroxyl group thereof.
The novolak resins are obtained by addition-condensing one or more given monomers as the main ingredient with one or more aldehydes in the presence of an acid catalyst.
Examples of the given monomers include hydroxylated aromatic compounds such as phenol, cresols, i.e., m-cresol, p-cresol, and o-cresol, xylenols, e.g., 2,5-xylenol, 3,5-xylenol, 3,4-xylenol, and 2,3-xylenol, alkylphenols, e.g., m-ethylphenol, p-ethylphenol, o-ethylphenol, p-t-butylphenol, p-octylphenol, and 2,3,5-trimethylphenol, alkoxyphenols, e.g., p-methoxyphenol, m-methoxyphenol, 3,5-dimethoxyphenol, 2-methoxy-4-methylphenol, m-ethoxyphenol, p-ethoxyphenol, m-propoxyphenol, p-propoxyphenol, m-butoxyphenol, and p-butoxyphenol, dialkylphenols, e.g., 2-methyl-4-isopropylphenol, and other hydroxylated aromatics including m-chlorophenol, p-chlorophenol, o-chlorophenol, dihydroxybiphenyl, bisphenol A, phenylphenol, resorcinol, and naphthol. These compounds may be used alone or as a mixture of two or more thereof. The main monomers for novolak resins should not be construed as being limited to the above examples.
Examples of the aldehydes include formaldehyde, paraformaldehyde, acetaldehyde, propionaldehyde, benzaldehyde, phenylacetaldehyde, xcex1-phenylpropionaldehyde, xcex2-phenylpropionaldehyde, o-hydroxybenzaldehyde, m-hydroxybenzaldehyde, p-hydroxybenzaldehyde, o-chlorobenzaldehyde, m-chlorobenzaldehyde, p-chlorobenzaldehyde, o-nitrobenzaldehyde, m-nitrobenzaldehyde, p-nitrobenzaldehyde, o-methylbenzaldehyde, m-methylbenzaldehyde, p-methylbenzaldehyde, p-ethylbenzaldehyde, p-n-butylbenzaldehyde, furfural, chloroacetaldehyde, and acetals derived from these, such as chloroacetaldehyde diethyl acetal. Preferred of these is formaldehyde.
These aldehydes may be used alone or in combination of two or more thereof. Examples of the acid catalyst include hydrochloric acid, sulfuric acid, formic acid, acetic acid, and oxalic acid.
The addition amount of the alkali-soluble resin containing no acid-decomposable groups is preferably up to 50% by weight, more preferably up to 30% by weight, most preferably up to 20% by weight, based on the total amount of the alkali-soluble resin containing no acid-decomposable groups and the alkali-soluble resin containing an acid-decomposable group.
The photo-acid generator (c) is a compound which generates an acid by the irradiation of an actinic ray or radiation.
Examples of such photo-acid generators usable in combination with the specific photo-acid generator include photoinitiators for cationic photopolymerization, photoinitiators for radical photopolymerization, photodecolorants for dyes, optical color changers, and known compounds which generate an acid by the action of known light which is used in microresists, etc. such as ultraviolet ray having a wavelength of 400 to 200 nm, far-ultraviolet ray, especially, g-line, h-line, i-line, KrF exima laser light), ArF exima laser light, electron beam, X-ray, molecule ray, or ion beam. These photo-acid generators may be suitably used either alone or as a mixture of two or more thereof.
Specific examples thereof include onium salts such as: the diazonium salts described in, e.g., S. I. Schlesinger, Photogr. Sci. Eng., 18, 387 (1974) and T. S. Bal et al., Polymer, 21, 423 (1980); the ammonium salts described in, e.g., U.S. Pat. Nos. 4,069,055 and 4,069,056, U.S. Reissued Pat. No. 27,992, and Japanese Patent Application No. 3-140,140; the phosphonium salts described in, e.g., D. C. Necker et al., Macromolecules, 17, 2468 (1984), C. S. Wen et al., Teh, Proc. Conf. Rad. Curing ASIA, p. 478 Tokyo, October (1988), and U.S. Pat. Nos. 4,069,055 and 4,069,056; the iodonium salts described in, e.g., J. V. Crivello et al., Macromolecules, 10 (6), 1307 (1977), Chem. and Eng. News, November 28, p. 31 (1988), European Patent 104,143, U.S. Pat. Nos. 339,049 and 410,201, JP-A-2-150,848, and JP-A-2-296,514; the sulfonium salts described in, e.g., J. V. Crivello et al., Polymer J., 17, 73 (1985), J. V. Crivello et al., J. Org. Chem., 43, 3055 (1978), W. R. Watt et al., J. Polymer Sci., Polymer Chem. Ed., 22, 1789 (1984), J. V. Crivello et al., Polymer Bull., 14, 279 (1985), J. V. Crivello et al., Macromolecules, 14 (5), 1141 (1981), J. V. Crivello et al., J. Polymer Sci., Polymer Chem. Ed., 17, 2877 (1979), European Patents 370,693, 3,902,114, 233,567, 297,443, and 297,442, U.S. Pat. Nos. 4,933,377, 161,811, 410,201, 339,049, 4,760,013, 4,734,444, and 2,833,827, and German Patents 2,904,626, 3,604,580, and 3,604,581; the selenonium salts described in, e.g., J. V. Crivello et al., Macromolecules, 10 (6), 1307 (1977) and J. V. Crivello et al., J. Polymer Sci., Polymer Chem. Ed., 17, 1047 (1979); and the arsonium salts described in, e.g., C. S. Wen et al., Teh, Proc. Conf. Rad. Curing ASIA, p. 478 Tokyo, October (1988). Specific examples thereof further include the organohalogen compounds described in, e.g., U.S. Pat. No. 3,905,815, JP-B-46-4605 (the term xe2x80x9cJP-Bxe2x80x9d as used herein means an xe2x80x9cexamined Japanese patent publicationxe2x80x9d), JP-A-48-36281, JP-A-55-32070, JP-A-60-239736, JP-A-61-169835, JP-A-61-169837, JP-A-62-58241, JP-A-62-212401, JP-A-63-70243, and JP-A-63-298339; the organometallic compound/organic halide combinations described in, e.g., K. Meier et al., J. Rad. Curing, 13 (4), 26 (1986), T. P. Gill et al., Inorg. Chem., 19, 3007 (1980), D. Astruc, Acc. Chem. Res., 19 (12), 377 (1896), and JP-A-2-161445; the photo-acid generators having an o-nitrobenzyl type protective group described in, e.g., S. Hayase et al., J. Polymer Sci., 25, 753 (1987), E. Reichmanis et al., J. Polymer Sci., Polymer Chem. Ed., 23, 1 (1985), Q. Q. Zhu et al., J. Photochem., 36, 85, 39, 317 (1987), B. Amit et al., Tetrahedron Lett., (24) 2205 (1973), D. H. R. Barton et al., J. Chem Soc., 3571 (1965), P. M. Collins et al., J. Chem. Soc., Perkin I, 1695 (1975), M. Rudinstein et al., Tetrahedron Lett., (17), 1445 (1975), J. W. Walker et al., J. Am. Chem. Soc., 110, 7170 (1988), S. C. Busman et al., J. Imaging Technol., 11 (4), 191 (1985), H. M. Houlihan et al., Macromolecules, 21, 2001 (1988), P. M. Collins et al., J. Chem. Soc., Chem. Commun., 532 (1972), S. Hayase et al., Macromolecules, 18, 1799 (1985), E. Reichmanis et al., J. Electrochem. Soc., Solid State Sci. Technol., 130 (6), F. M. Houlihan et al., Macromolecules, 21, 2001 (1988), European Patents 0,290, 750, 046,083, 156,535, 271,851, and 0,388,343, U.S. Pat. Nos. 3,901,710 and 4,181,531, JP-A-60-198538, and JP-A-53-133022; compounds which photodecompose to generate a sulfonic acid and are represented by the iminosulfonates described in, e.g., M. Tunooka et al., Polymer Preprints, Japan, 35 (8), G. Berner et al., J. Rad. Curing, 13 (4), W. J. Mijs et al., Coating Technol., 55 (697), 45 (1983), Akzo, H. Adachi et al., Polymer Preprints, Japan, 37 (3), European Patents 0,199,672, 84,515, 199,672, 044,115, and 0,101,122, U.S. Pat. Nos. 618,564, 4,371,605, and 4,431,774, JP-A-64-18143, JP-A-2-245756, and Japanese Patent Application No. 3-140109; and the disulfone compounds described in, e.g., JP-A-61-166544.
Further, a compound obtained by incorporating such groups or compounds which generate an acid by the action of light into the backbone or side chains of a polymer can be used. Examples of this polymeric compound are given in, e.g., M. E. Woodhouse et al., J. Am. Chem. Soc., 104, 5586 (1982), S. P. Pappas et al., J. Imaging Sci., 30 (5), 218 (1986), S. Kondo et al., Makromol. Chem., Rapid Commun., 9,625 (1988), Y. Yamada et al., Makromol. Chem., 152, 153, 163 (1972), J. V. Crivello et al., J. Polymer Sci., Polymer Chem. Ed., 17, 3845 (1979), U.S. Pat. No. 3,849,137, German Patent 3,914,407, JP-A-63-26653, JP-A-55-164824, JP-A-62-69263, JP-A-63-146038, JP-A-63-163452, JP-A-62-153853, and JP-A-63-146029.
Also usable are the compounds which generate an acid by the action of light as described in, e.g., V. N. R. Pillai, Synthesis, (1), 1 (1980), A. Abad et al., Tetrahedron Lett., (47) 4555 (1971), D. H. R. Barton et al., J. Chem. Soc., (C), 329 (1970), U.S. Pat. No. 3,779,778, and European Patent 126,712.
Of the optionally usable compounds enumerated above which generate an acid upon irradiation with actinic rays or a radiation, especially effective compounds are explained below.
(1) Trihalomethyl-substituted oxazole derivatives represented by the following formula (PAG1) and trihalomethyl-substituted s-triazine derivatives represented by the following general formula (PAG2). 
In the above formulae, R201 represents a substituted or unsubstituted aryl or alkenyl group; R202 represents a substituted or unsubstituted aryl, alkenyl, or alkyl group (preferably those having 6 to 16 carbon atoms, e.g., phenyl, halogen-substituted phenyl, a C1-4 alkyl- or alkoxy-phenyl, napthyl, styryl) or xe2x80x94C(Y)3; and Y represents a chlorine or bromine atom.
Specific examples thereof are given below, but the compounds represented by general formula (PAG1) or (PAG2) should not be construed as being limited thereto. 
(2) Iodonium salts represented by the following general formula (PAG3) and sulfonium salts represented by the following general formula (PAG4). 
In the above formulae, Ar1 and Ar2 each independently represents a substituted or unsubstituted aryl group (preferably those having 6 to 18 carbon atoms). Examples of the substituents include an alkyl group, a haloalkyl group, a cycloalkyl group, an aryl group, an alkoxy group, a nitro group, a carboxyl group, an alkoxycarbonyl group, a hydroxy group, a mercapto group, and a halogen atom, and preferred are a halogen atom, an alkyl group such as methyl, ethyl, propyl and butyl, an alkoxy group such as methoxy, ethoxy, propoxy and butoxy, and a trifluoromethyl group. Preferred examples of the unsubstituted aryl group include those having 6 to 10 carbon atoms such as phenyl and naphtyl.
R203, R204, and R205 each independently represents a substituted or unsubstituted alkyl or aryl group, and preferably represents an aryl group having 6 to 14 carbon atoms, an alkyl group having 1 to 8 carbon atoms, or a substitution derivative thereof. Preferred substituents for the aryl group include alkoxy groups having 1 to 8 carbon atoms, alkyl groups having 1 to 8 carbon atoms, nitro, carboxyl, hydroxy, and halogen atoms. Preferred substituents for the alkyl group include alkoxy groups having 1 to 8 carbon atoms, carboxyl, and alkoxycarbonyl groups.
Zxe2x88x92 represents a counter anion, specifically a perfluoroalkanesulfonate anion, e.g., CF3SO3xe2x88x92, or a pentafluorobenzenesulfonate anion.
Two of R203, R204, and R205 may be bonded to each other through a single bond or substituent thereof. Ar1 and Ar2 may be bonded to each other likewise.
It is preferred to use a photo-acid generator which does not change the performance (T-Top formation, change of line width, and the like) so much with a lapse of time from exposure to heat treatment. Examples thereof include those of formula (PAG3) or (PAG4) in which Ar1, Ar2, and R203 to R205 are a substituted or unsubstituted aryl group, and Zxe2x88x92 is one capable of forming an acid having relatively small diffusibility in the resist film with irradiation of actinic rays or radiation.
Specifically, Zxe2x88x92 is an anion of benzene sulfonic acid, naphthalene sulfonic acid, or anthracene sulfonic acid, having at least one group selected from the group consisting of a branched or cyclic, alkyl or alkoxy group having 8 carbon atoms or more, at least two groups selected from the group consisting of a linear, branched or cyclic, alkyl or alkoxy group having 4 to 7 carbon atoms, or at least three groups selected from the group consisting of a linear or branched, alkyl or alkoxy group having 1 to 3 carbon atoms.
Specific examples thereof are given below, but the compounds represented by general formula (PAG3) or (PAG4) should not be construed as being limited thereto. 
The onium salts represented by general formulae (PAG3) and (PAG4) are known. They can be synthesized, for example, by the methods described in, e.g., J. W. Knapczyk et al., J. Am. Chem. Soc., 91, 145 (1969), A. L. Maycok et al., J. Org. Chem., 35, 2535 (1970), E. Goethas et al., Bull. Soc. Chem. Belg., 73, 546 (1964), H. M. Leicester, J. Ame. Chem. Soc., 51, 3587 (1929), J. V. Crivello et al., J. Polym. Chem. Ed., 18, 2677 (1980), U.S. Pat. Nos. 2,807,648 and 4,247,473, and JP-A-53-101331.
(3) Disulfone derivatives represented by the following general formula (PAG5) and iminosulfonate derivatives represented by the following general formula (PAG6). 
In the above formulae, Ar3 and Ar4 each independently represents a substituted or unsubstituted aryl group; R206 represents a substituted or unsubstituted alkyl or aryl group; and A represents a substituted or unsubstituted alkylene, alkenylene, or arylene group.
The substituted aryl group as Ar3 and Ar4 preferably has 6 to 18 carbon atoms. Examples of the substituent include a halogen atom, an alkyl group such as methyl, ethyl, propyl and butyl, an alkoxy group such as methoxy, ethoxy, propoxy and butoxy, and a trifluoromethyl group. Preferred examples of the unsubstituted aryl group as Ar3 and Ar4 include those having 6 to 10 carbon atoms such as phenyl and naphthyl.
The unsubstituted alkyl group as R206 is preferably an alkyl group having 1 to 10 carbon atoms such as methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, and decyl. The unsubstituted aryl group as R206 is preferably an aryl group having 6 to 10 carbon atoms such as phenyl and naphthyl. The substituted alkyl and aryl groups preferably have 6 to 14 carbon atoms. Examples of the substituent include an alkyl group, an alkoxy group, a cycloalkyl group and a trifluoromethyl group, each having 1 to 8 carbon atoms, and a halogen atom.
The unsubstituted alkylene, alkenylene, or arylene group as A preferably has 2 to 10 carbon atoms, and the substituted alkylene, alkenylene, or arylene group as A preferably has 2 to 14 carbon atoms. Examples of the substituent include an alkyl group, an alkoxy group, a cycloalkyl group, each having 1 to 6 carbon atoms, a phenyl group, a trifluoromethyl group, and a halogen atom.
Specific examples thereof are given below, but the compounds represented by general formula (PAG5) or (PAG6) should not be construed as being limited thereto. 
In the present invention, it is preferred that Compound (c) which generates an acid with irradiation of actinic ray or radiation is selected from the onium salts, disulfones, 4-position DNQ sulfonates, and triazine compounds.
The addition amount of Compound (c) is generally from 0.001 to 40% by weight, preferably from 0.01 to 20% by weight, more preferably from 0.1 to 5% by weight, based on the total weight (excluding a coating solvent) of the positive photoresist composition. If the amount is less than 0.001% by weight, the sensitivity is reduced, and if it exceeds 40% by weight, light absorption of the resist is increased to thereby deteriorate the profile or reduce process (especially bake) margin.
The composition of the present invention can contain organic basic compounds, which improve the stability during storage and reduce the change in line width attributable to PED.
Desirable organic basic compounds usable in the present invention are compounds which are more strongly basic than phenol, in particular, nitrogen-containing basic compounds.
Preferred chemical environments include structures represented by the following formulae (A) to (E). 
In formula (A), R250, R251, and R252 may be the same or different and each represents a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, an aminoalkyl group having 1 to 6 carbon atoms, a hydroxyalkyl group having 1 to 6 carbon atoms, or a substituted or unsubstituted aryl group having 6 to 20 carbon atoms, provided that R254 and R255 may be bonded to each other to form a ring. 
(In formula (E), R253, R254, R255, and R256 may be the same or different and each represents an alkyl group having 1 to 6 carbon atoms.)
Preferred organic basic compounds are nitrogen-containing basic compounds having, per molecule, two or more nitrogen atoms having different chemical environments. Especially preferred are compounds containing both at least one substituted or unsubstituted amino group and at least one nitrogen-containing ring structure and compounds having at least one alkylamino group. Examples of such preferred compounds include substituted or unsubstituted guanidine, substituted or unsubstituted aminopyridine, substituted or unsubstituted aminoalkylpyridines, substituted or unsubstituted aminopyrrolidine, substituted or unsubstituted indazole, substituted or unsubstituted pyrazole, substituted or unsubstituted pyrazine, substituted or unsubstituted pyrimidine, substituted or unsubstituted purine, substituted or unsubstituted imidazoline, substituted or unsubstituted pyrazoline, substituted or unsubstituted piperazine, substituted or unsubstituted aminomorpholine, and substituted or unsubstituted aminoalkylmorpholines. Preferred substituents include amino, aminoalkyl groups, alkylamino groups, aminoaryl groups, arylamino groups, alkyl groups, alkoxy groups, acyl groups, acyloxy groups, aryl groups, aryloxy groups, nitro, hydroxy, and cyano. Specific examples of especially preferred organic basic compounds include guanidine, 1,1-dimethylguanidine, 1,1,3,3-tetramethylguanidine, 2-aminopyridine, 3-aminopyridine, 4-aminopyridine, 2-dimethylaminopyridine, 4-dimethylaminopyridine, 2-diethylaminopyridine, 2-(aminomethyl)pyridine, 2-amino-3-methylpyridine, 2-amino-4-methylpyridine, 2-amino-5-methylpyridine, 2-amino-6-methylpyridine, 3-aminoethylpyridine, 4-aminoethylpyridine, 3-aminopyrrolidine, piperazine, N-(2-aminoethyl)piperazine, N-(2-aminoethyl)piperidine, 4-amino-2,2,6,6-tetramethylpiperidine, 4-piperidinopiperidine, 2-iminopiperidine, 1-(2-aminoethyl)pyrrolidine, pyrazole, 3-amino-5-methylpyrazole, 5-amino-3-methyl-1-p-tolylpyrazole, pyrazine, 2-(aminomethyl)-5-methylpyrazine, pyrimidine, 2,4-diaminopyrimidine, 4,6-dihydroxypyrimidine, 2-pyrazoline, 3-pyrazoline, N-aminomorpholine, and N-(2-aminoethyl)morpholine. However, the organic basic compounds usable in the present invention should not be construed as being limited to these examples.
Those nitrogen-containing basic compounds may be used alone or in combination of two or more thereof. The use amount of the nitrogen-containing basic compounds is usually from 0.001 to 10 parts by weight, preferably from 0.01 to 5 parts by weight, per 100 parts by weight of the photosensitive resin composition (excluding the solvent). If the amount thereof is smaller than 0.001 part by weight, the effects of the present invention cannot be obtained. On the other hand, if it exceeds 10 parts by weight, reduced sensitivity and impaired developability at unexposed parts are liable to be caused.
The chemically amplified positive resist composition can further contain a surfactant, dye, pigment, plasticizer, photosensitizer, or a compound having at least two phenolic OH groups which accelates the solubility in a developing solution, if desired.
Examples of the surfactant include nonionic surfactants such as polyoxyethylene alkyl ethers, e.g., polyoxyethylene lauryl ether, polyoxyethylene stearyl ether, polyoxyethylene cetyl ether, and polyoxyethylene oleyl ether, polyoxyethylene alkylaryl ethers, e.g., polyoxyethylene octylphenol ether and polyoxyethylene nonylphenol ether, polyoxyethylene/polyoxypropylene block copolymers, sorbitan/fatty acid esters, e.g., sorbitan monolaurate, sorbitan monopalmitate, sorbitan monostearate, sorbitan monooleate, sorbitan trioleate, and sorbitan tristearate, and polyoxyethylene-sorbitan/fatty acid esters, e.g., polyoxyethylene sorbitan monolaurate, polyoxyethylene sorbitan monopalmitate, polyoxyethylene sorbitan monostearate, polyoxyethylene sorbitan trioleate, and polyoxyethylene sorbitan tristearate; fluorochemical surfactants such as F-Top EF301, EF303, and EF352 (manufactured by New Akita Chemical Company, Japan), Megafac F171 and F173 (manufactured by Dainippon Ink and Chemicals, Inc., Japan), Fluorad FC430 and FC431 (manufactured by Sumitomo 3M Ltd., Japan), Asahi Guard AG710 and Surflon S-382, SC101, SC102, SC103, SC104, SC105, and SC106 (manufactured by Asahi Glass Co., Ltd., Japan); organosiloxane polymer KP341 (manufactured by Shin-Etsu Chemical Co., Ltd., Japan); and acrylic or methacrylic (co)polymers Polyflow No. 75 and No. 95 (manufactured by Kyoeisha Chemical Co., Ltd., Japan). The surfactant may be added alone or in combination of two or more thereof. The preferred amount of the surfactant is from 0.0005 to 0.01 parts by weight per 100 parts by weight of the composition (excluding a solvent) of the present invention.
Dyes suitable for use in the present invention are oil-soluble dyes and basic dyes. Examples thereof include Oil Yellow #101, Oil Yellow #103, Oil Pink #312, Oil Green BG, Oil Blue BOS, Oil Blue #603, Oil Black BY, Oil Black BS, Oil Black T-505 (all manufactured by Orient Chemical Industries Ltd., Japan), crystal violet (CI 42555), methyl violet (CI 42535), rhodamine B (CI 45170B), malachite green (CI 42000), and methylene blue (CI 52015).
Spectral sensitizers such as those given below may be further added to sensitize the photo-acid generator used so as to exhibit absorption in a region of longer wavelengths than far ultraviolet, whereby the photosensitive composition of the present invention can be rendered sensitive to an i- or g-line. Examples of spectral sensitizers suitable for use in the present invention include benzophenone, p,pxe2x80x2-tetramethyldiaminobenzophenone, p,pxe2x80x2-tetraethylethylaminobenzophenone, 2-chlorothioxanthone, anthrone, 9-ethoxyanthracene, anthracene, pyrene, perylene, phenothiazine, benzil, acridine orange, benzoflavin, cetoflavin T, 9,10-diphenylanthracene, 9-fluorenone, acetophenone, phenanthrene, 2-nitrofluorene, 5-nitroacenaphthene, benzoquinone, 2-chloro-4-nitroaniline, N-acetyl-p-nitroaniline, p-nitroaniline, N-acetyl-4-nitro-1-naphthylamine, picramide, anthraquinone, 2-ethylanthraquinone, 2-tert-butylanthraquinone, 1,2-benzanthraquinone, 3-methyl-1,3-diaza-1,9-benzanthrone, dibenzalacetone, 1,2-naphthoquinone, 3,3xe2x80x2-carbonylbis(5,7-dimethoxycarbonylcoumarin), and coronene. However, the spectral sensitizers usable in the present invention should not be construed as being limited to these examples.
As the compounds having at least two phenolic OH groups which accelate the solubility in a developing solution, polyhydroxy compounds can be exemplified. Preferred examples thereof include phenols, resorcin, phloroglucin, phloroglucide, 2,3,4-trihydroxybenzophenone, 2,3,4,4xe2x80x2-tetrahydroxybenzophenone, xcex1,xcex1xe2x80x2,xcex1xe2x80x3-tris(4-hydroxyphenyl)-1,3,5-triisopropylbenzene, tris(4-hydroxyphenyl)methane, tris(4-hydroxyphenyl)ethane, and 1,1xe2x80x2-bis (4-hydroxypheyl)cyclohexane.
For application to a substrate, the photosensitive composition of the present invention is used in the form of a solution in a solvent (component (d)) in which the ingredients described above dissolve. Preferred examples of the solvent include ethylene dichloride, cyclohexanone, cyclopentanone, 2-heptanone, xcex3-butyrolactone, methyl ethyl ketone, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, 2-methoxyethyl acetate, ethylene glycol monoethyl ether acetate, propylene glycol monomethyl ether, propylene glycol monomethyl ether acetate, toluene, ethyl acetate, methyl lactate, ethyl lactate, methyl methoxypropionate, ethyl ethoxypropionate, methyl pyruvate, ethyl pyruvate, propyl pyruvate, N,N-dimethylformamide, dimethyl sulfoxide, N-methylpyrrolidone, and tetrahydrofuran. These solvents may be used alone or as a mixture thereof. The solvent can be added in such an amount that the solid components in the resist composition is generally from 1 to 40% by weight, preferably from 7 to 25% by weight based on the resist composition.
A satisfactory resist pattern can be obtained by applying the photosensitive composition described above on a substrate such as those for use in the production of precision integrated-circuit elements (e.g., silicon/silicon dioxide coating) by an appropriate coating means, e.g., a spinner or coater, exposing the coating to light through a mask, and then baking and developing the coating.
As a developing solution for the photosensitive composition of the present invention, use can be made of an alkaline aqueous solution of an inorganic alkali, e.g., sodium hydroxide, potassium hydroxide, sodium carbonate, sodium silicate, sodium metasilicate, or ammonia water, a primary amine, e.g., ethylamine or n-propylamine, a secondary amine, e.g., diethylamine or di-n-butylamine, a tertiary amine, e.g., triethylamine or methyldiethylamine, an alcoholamine, e.g., dimethylethanolamine or triethanolamine, a quaternary ammonium salt, e.g., tetramethylammonium hydroxide or tetraethylammonium hydroxide, a cyclic amine, e.g., pyrrole or piperidine, or the like.
The present invention will be explained below in more detail by reference to Examples, but the invention should not be construed as being limited thereto.
The present invention will be explained below in more detail by reference to Examples, but the invention should not be construed as being limited thereto.